Bela Bartok's
Music for Strings, Percussion and Celesta, specifically
Andante tranquillo and
Adagio, though parts of
Allegro molto might also qualify.
Samual Barbar's
Adagio for Strings, Krzystof Penderecki's
Threnody For The Victims Of Hiroshima For 52 Stringed Instruments and
De Natura Sonoris II For Orchestra (which sound very much like the music from
Altered States by John Corigliano),
Space Requiem by Stomu Yamash'ta, and
Title music for the movie The Bounty by Vangelis Papathanassiou are honorable mentions.